Aluminum alloy-steel bearing and method of making same

ABSTRACT

Bimetallic bearing material comprising aluminum alloys consisting of silicon, cadmium, copper, magnesium, and the balance aluminum, bonded directly on steel backings, are heat treated to effect improved hardness and fatigue resistance. The heat treatment comprises solution heating said bearing material at temperatures ranging from 900* F. to 975* F. for at least 15 seconds but not exceeding 80 seconds, after which it is rapidly quenched in a fluid medium having a maximum temperature of 100* F., followed by precipitation heat treatment at about 350* F. for ten hours.

[451 Mar. 28, 1972 154] ALUMINUM ALLOY-STEEL BEARING AND METHOD OFMAKING SAME [72] Inventors: George R. Kingsbury, Cleveland;

Raymond L. Slater, Novelty, both of Ohio [73] Assignee: CleviteCorporation [22] Filed: Sept. 25, 1969 [21] App]. No.: 861,196

[52] US. Cl ..148/127, 29/1484, 29/1495, 29/1962, 148/12, l48/l2.7,148/34 [51] Int. Cl ..B21d 53/10, C2ld 1/46, C2ld 9/40 [58] FieldofSearch ..148/l2,12.7,l27, 15,18, 148/34, 159; 29/1962, 148.4, 149.5

[56] References Cited UNlTED STATES PATENTS 3,268,369 8/1966 Haugen..29/196.2 X

2,807,540 9/1957 Schluchter ..75/142 OTHER PUBLICATIONS Metals Handbook,Vol. 2, 8th Ed., 1964, pages 64- 66 Primary Examiner-Charles N. LovellAttorney-Eber J. Hyde [57] ABSTRACT Bimetallic bearing materialcomprising aluminum alloys consisting of silicon, cadmium, copper,magnesium, and the balance aluminum, bonded directly on steel backings,are heat treated to efi'ect improved hardness and fatigue resistance.The heat treatment comprises solution heating said bearing material attemperatures ranging from 900 F. to 975 F. for at least 15 seconds butnot exceeding 80 seconds, after which it is rapidly quenched in a fluidmedium having a maximum temperature of 100 F., followed by precipitationheat treatment at about 350 F. for ten hours.

6 Claims, N0 Drawings Slater et al. ..29/196.2 X Y ALUMINUM ALLOY-STEELBEARING AND METHOD OF MAKING SAME The present invention relates to abearing comprising aluminum alloy directly bonded on a steel backing.More specifibearings comprising aluminum alloys directly bonded ontosteel supports or backings. The aluminum alloy consists of aluminumhaving small amounts of silicon, cadmium, copper, and magnesium. Thesteel backing can be any of a number of low carbon steels.

Several methods for improving strength and fatigue resistance aredisclosed in the prior art. Of note is the method disclosed in U.S. Pat.No. 3,268,369 which teaches, among other things, the step ofv heatingthe finished bearing in a nonoxidizing atmosphere at temperaturesranging from 750 F. to just below the eutectic melting point of thealuminum alloy. The above-mentioned patent further teaches that theheating period can be as short as five minutes, but can be longer.

It has been found that solution heat treatments in the order of fiveminutes and longer are not necessary. in fact, solution heat treatmentin the order of 15 seconds is quite satisfactory for obtaining thedesired properties of fatigue resistance and strength. Furthermore, heattreatment of finished bearings may be undesirable because of damage tothe finely finished bearing surfaces.

It is an object of this invention to provide a bimetallic strip ofbearing material and the method of making same, from which low cost,strong, and fatigue resistant bearings are made.

Another object of the invention is to provide a heat treatment forhearing material, in strip, blank, or semifinished bearing form, therebyimproving the strength and fatigue resistance of the finished bearings.

A further object of the invention is to provide high quality bearingssuitable for use under high loadings and speed conditrons.

Other objects and advantages will become more apparent from thefollowing description.

In carrying out the process of the invention, steel of the typecommercially known as SAE 1010 or 1008 may be used as the material forthe backing support, though other steel types may be used. Low carbonsteel is preferred because it endures a greater rolling reduction whichresults in an improved bond. Also, it has lower initial hardness and isless subject to cold working during cladding and forming.

As to the aluminum alloy, it is directly bonded onto the steel backingto form the bearing material in accordance with the method disclosed inU.S. Pat. No.- 3,300,838, assigned to the same assignee of the presentinvention. The heat-treatment response of the aluminum alloy is relatedto the copper and magnesium content, as well as the silicon content.Aluminum alloys having silicon 2-8 percent, cadmium 0.5-4 percent,copper 0.05-15 percent, magnesium 0.1-0.2 percent, and the balancealuminum, have proven very satisfactory and the invention contemplatesonly alloys having the above compositions. The thickness of the layer ofaluminum alloy and/or the overall thickness of the composite structure,i.e., the bearing material, depend on the intended use of the finishedbearing.

The bimetallic bearing material can be treated in strip, blank, orsemi-finished bearing form. When applied to the strip form, the steelbacked clad aluminum strip is attached to a pulling unit leading into amolten lead bath maintained at temperature ranging from 900 to 975 F.,preferably about 950 F. The strip is then pulled out at a speedpermitting it to be heated at said temperature range for a minimum timeof 15 seconds. Heat-up time takes usually about a minute. Thus, totalimmersion in the lead bath may take about seconds. As the strip is beingpulled out of the lead bath it is wiped to remove lead particles thatmay have occluded onto the surface. The strip is then quickly quenchedin a fluid medium such as water or oil having a maximum temperature ofl00 F preferably about 75 F. The time between removal from the lead bathto quenching should be such that the temperature of the strip is notallowed to drop below 850 F. Intervals in the order of 30 seconds areusually satisfactory. It should be emphasized that the drop intemperature prior to quenching is of important consideration. The shortheating cycle is sufficient to cause the copper, magnesium, and aportion of the silicon to go into solid solution with the aluminum underequilibrium conditions and rapid quenching is necessary to preserve acondition of super saturation.

After quenching, the strip is air dried and hardened by precipitationheat treatment at 350 F. for about ten hours in a recirculating airfurnace, or other heating means. A minimum hardness of 62 on theRockwell l5 T-scale is obtained for 0.010 inch thick aluminum alloyliner. The strip is then fabricated into bearings and the bearingsurface is machined and plated at the bearing surface with an overlayhaving thickness of 0.0004 to 0.0006 inches. The overlay comprisesgenerally a high lead alloy having copper and tin.

The above description alluded to a method of making and heat-treatingsimple sleeve bearings. If flange bearings are desired, then thebimetallic strip may be heat treated in the molten lead bath asdescribed above. After quenching, the bearing strip is cut into bearingblanks which are channelled, and roll-formed into shells. The formedbearings are then hardened by precipitation heat treatment in arecirculating air furnace at about 350 F. for 10 hours to a minimum R T62 hardness for a 0.010 inch thick alloy liner.

Other media for solution heat treatment can be utilized such as moltensalt baths. For example, the bimetallic strip can be cut into bearingblanks which are then placed in convenient means such as metal basketswhich can be lowered into the molten salt bath having a temperatureranging from 900-975 F. The blanks are then maintained at saidtemperature for a minimum of 15 seconds excluding heat-up time which isusually about one minute. The blanks are then quenched in a fluid mediumsuch as water (maximum temperature F.). Again, keeping in mind that theinterval between removing from the molten salt bath and the quenching issuch that the temperature of the blanks does not drop below 850 F.Normally, a delay time of up to 30 seconds is satisfactory. The blanksare then dried and precipitation hardened at about 350 F. for ten hoursin a recirculating air furnace. Bearings are then fabricated from thehardened blanks as described hereinbefore. As to flange bearings, theblanks are channelled and rollformed into shells after the solution heattreatment, then they are precipitation hardened at 350 F., as described.

For uniform results, the bimetallic strip is annealed at 650 F. for 30minutes prior to solution heat treatment.

Given below are some specific examples of making strong and fatigueresistance bearings from blank form utilizing solution heat treatment inmolten salt bath in accordance with the invention.

EXAMPLE I. DIESEL ROD BEARlNG An aluminum alloy having a composition of3.94 percent silicon, 1.0 percent cadmium, 0.13 percent copper, 0.14percent magnesium, and the balance aluminum, was directly bonded onto asteel backing (SAE 1010) having a thickness of 0.085 inches to form abimetallic strip having a thickness of 0.100 inch. The strip was cutinto blanks which were heated in a neutral molten salt bath at 950 F.for 65 seconds, 50 seconds were required for heat-up time. The blankswere then removed from the bath and rapidly quenched in water at 75 F.The blanks were then precipitation hardened by heating in an airrecirculating furnace at 350 F. for 10 hours. The alu- EXAMPLE II.DIESEL MAIN BEARING An aluminum alloy having the composition 3.70percent silicon, 1.l percent cadmium, 0.15 percent magnesium, 0.10percent copper, and the balance aluminum, was directly bonded onto anSAE 1010 steel backing (0.139 inch thick) to form a bimetallic bearingstrip of 0.166 inch thickness. The strip was cut into blanks which weresolution heat treated in a neutral molten salt bath at 950 F as done inExample 1. After precipitation hardening at 350 F. for hours, theaverage hardness of the aluminum alloy layer measured 69 on R T scale.The blanks were then fabricated into bearings having 0.156 inch wallthickness. Hardness of the aluminum alloy liner had an average of 70 onR ,,T scale. Similar to Example I, the bearing was plated with anover-lay (0.0005 inch thick) having the same composition.

Bearings having the same composition and thickness, but not solutionheat treated, had an average hardness of 48 on R T scale.

EXAMPLE III. DIESEL FLANGE MAIN BEARING An aluminum alloy having thesame composition of Example II was directly bonded on an SAE 1010 steelbacking (0.089 inch thick) to form a bimetallic bearing strip having 0.119 inch thickness. The strip was cut into blanks which were solutionheat-treated, similar to Examples I and II. The quenched blanks werethen formed into flange bearing halfshells which were precipitationhardened, as described in the previous examples. The aluminum alloylayer, was found to have an average hardness of 69 on R T scale. Theformed shells were then machined to a wall thickness of 0.102 inch,after which an over-lay of about 0.0005 inch was plated on the bearingsurface.

Bearings having the same composition and thickness, but not solutionheat treated, had an average hardness of 49 on R ,,T scale.

While there have been described what are considered to be the preferredembodiments of this invention, it will be obvious to those skilled inthe art that various changes and modifica tions may be made thereinwithout departing from the invention.

What is claimed is:

l. A method for making a bimetallic bearing having improved fatigueresistance and strength which comprises the steps of:

a. bonding to a steel backing a layer of aluminum alloy consisting ofsilicon 2 to 8 percent, cadmium 0.5 to 4 percent, copper 0.05 to 0.15percent, magnesium 0.1 to 0.2 percent, and the balance aluminum, to forma composite bearing material in strip or blank form;

b. heating the bearing material to a temperature of at least 900 F., butnot in excess of 975 F.;

c. maintaining the bearing material at said temperature for a period ofat least seconds but not over 80 sec.;

d. cooling rapidly the bearing material in a fluid medium having amaximum temperature of 100 F e. forming the desired shape of thebearing; and

f. heating the bearing at a temperature of about 350 F. for a period ofabout therefor 10 hours to effect precipitation hardening.

2. The method described in claim 1 in which in step (a) the bearingmaterial is made in strip form, in which in step (b) the bearingmaterial is heated in molten lead bath having a temperature range offrom 900to 975 F. and m which In step (d) the fluid medium is waterhaving a maximum temperature of 100 F.

3. A method for improving fatigue resistance and strength of abimetallic bearing which comprises the steps of:

a. bonding directly to a steel backing a layer of aluminum alloyconsisting of silicon 2 to 8 percent, cadmium 0.5 to 4.0 percent, copper0.05 to 0.15 percent, magnesium 0.1 to 0.2 percent, and the balancealuminum, to form a composite bearing material in strip or blank form;

b. annealing said bearing material at a temperature of about 650 F. forabout 30 minutes;

0. heating said bearing material to a temperature ranging from 900 to975 F.;

d. maintaining said material at said temperature for at least 15seconds, but not over seconds;

e. cooling rapidly the bearing material in a fluid medium having amaximum temperature of F f. heating the bearing material at atemperature of about 350 F. for not over 10 hours to effectprecipitation hardening;

g. forming the desired shape of the bearing.

4. The method as described in claim 3 in which in step (a) the bearingmaterial is made in strip form; in which in step (c) the bearingmaterial is heated in a medium selected from the group consisting ofmolten lead and neutral molten salt, and in which in step (e) the fluidmedium is water having a maximum temperature of 100 F.

5. A method for improving fatigue resistance and strength of abimetallic bearing which comprises the steps of:

a. bonding directly to a low carbon steel backing a layer of aluminumalloy consisting of silicon 2 to 8 percent, cadmium 0.5 to 4.0 percent,copper 0.05 to 0.15 percent, magnesium 0.1 to 0.2 percent, and thebalance aluminum, to form a composite bearing material;

b. annealing said bearing material at a temperature of about 650 F. forabout 30 minutes;

c. cutting said annealed bearing material into bearing blanks;

d. heating said bearing blanks to a temperature ranging from 900 to 975F.;

e. maintaining said bearing blanks at said temperature for at least 15seconds, but not over 80 seconds;

f. cooling rapidly the bearing blanks in a fluid medium having a maximumtemperature of 100 F.;

g. cleaning and drying said bearing blanks;

h. heating said blanks at a temperature of 350 F. for 10 hours to efiectprecipitation hardening;

i. forming the desired shape of the bearing.

6. The method as described in claim 5 in which in step (d) the bearingblanks are heated in neutral molten salt bath having a temperature rangeof from 900 to 975 F and in which in step (f) the fluid medium is waterhaving a maximum temperature of 100 F.

2. The method as described in claim 1 in which in step (a) the bearingmaterial is made in strip form, in which in step (b) the bearingmaterial is heated in molten lead bath having a temperature range offrom 900*to 975* F. and in which in step (d) the fluid medium is waterhaving a maximum temperature of 100* F.
 3. A method for improvingfatigue resistance and strength of a bimetallic bearing which comprisesthe steps of: a. bonding directly to a steel backing a layer of aluminumalloy consisting of silicon 2 to 8 percent, cadmium 0.5 to 4.0 percent,copper 0.05 to 0.15 percent, magnesium 0.1 to 0.2 percent, and thebalance aluminum, to form a composite bearing material in strip or blankform; b. annealing said bearing material at a temperature of about 650*F. for about 30 minutes; c. heating said bearing material to atemperature ranging from 900 to 975* F.; d. maintaining said material atsaid temperature for at least 15 seconds, but not over 80 seconds; e.cooling rapidly the bearing material in a fluid medium having a maximumtemperature of 100* F.; f. heating the bearing material at a temperatureof about 350* F. for not over 10 hours to effect precipitationhardening; g. forming the desired shape of the bearing.
 4. The method asdescribed in claim 3 in which in step (a) the bearing material is madein strip form; in which in step (c) the bearing material is heated in amedium selected from the group consisting of molten lead and neutralmolten salt, and in which in step (e) the fluid medium is water having amaximum temperature of 100* F.
 5. A method for improving fatigueresistance and strength of a bimetallic bearing which comprises thesteps of: a. bonding directly to a low carbon steel backing a layer ofaluminum alloy consisting of silicon 2 to 8 percent, cadmium 0.5 to 4.0percent, copper 0.05 to 0.15 percent, magnesium 0.1 to 0.2 percent, andthe balance aluminum, to form a composite bearing material; b. annealingsaid bearing material at a temperature of about 650* F. for about 30minutes; c. cutting said annealed bearing material into bearing blanks;d. heating said bearing blanks to a temperature ranging from 900* to975* F.; e. maintaining said bearing blanks at said temperature for atleast 15 seconds, but not over 80 seconds; f. cooling rapidly thebearing blanks in a fluid medium having a maximum temperature of 100*F.; g. cleaning and drying said bearing blanks; h. heating said blanksat a temperature of 350* F. for 10 hours to effect precipitationhardening; i. forming the desired shape of the bearing.
 6. The method asdescribed in claim 5 in which in step (d) the bearing blanks are heatedin neutral molten salt bath having a temperature range of from 900* to975* F., and in which in step (f) the fluid medium is water having amaximum temperature of 100* F.